Coaxial cannula provided with a sealing element

ABSTRACT

A coaxial cannula for extracting samples from tissue having a biopsy needle unit provided with a space for sample extraction and a sample separation unit that coaxially encompasses the biopsy needle on an external wall and that is longitudinally movable. The coaxial cannula includes a sealing element that is arranged on the proximal end thereof and closes the space between the internal wall of the coaxial cannula and the external wall of the sample separation unit. The sealing element opens an air outlet when the biopsy needle unit is inserted, and prevents air intake when the biopsy needle unit is positioned and vacuum is produced in the internal chamber of the biopsy needle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. §371 application of InternationalApplication No. PCT/EP04/03327, filed Mar. 29, 2004, which claimspriority to German Patent Application No. 20305093.2, filed Mar. 29,2003, the entireties of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Known from DE GMS 202 09 525.8 is a coaxial cannula that can be insertedinto tissue and in which a biopsy needle unit can be employed. A seal isprovided between the interior wall of the coaxial cannula and theexterior wall of the biopsy needle unit in order to, first, preventfluid from escaping and, second, to make it possible to create a vacuumin the tissue to be biopsied. DE GMS 202 09 525.8 states that thesealing function of the seal must be created such that it prevents airfrom entering or escaping and also prevents fluid from escaping.

Such a seal has led to problems in practice. When inserting the biopsyneedle unit into the coaxial cannula and during subsequent positioningof the needle unit, the air that has penetrated into the coaxial cannulaas a result of the insertion process is sealed in and air bubbles formthat cause problems with the ultrasound or MR images made while theneedle is being positioned so that precise positioning is not possibledue to the air occlusions.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is to solve this problem.

The invention relates to a coaxial cannula that can be employed intissue, in which for removing tissue are a biopsy needle unit withspecimen removal space and a longitudinally movable specimen separatingdevice that coaxially encloses the biopsy needle on the exterior wall,and whereby the coaxial cannula has on its proximal end a sealingelement that encloses the space between the interior wall of the coaxialcannula and the exterior wall of the specimen separating device.

The object is attained in that the sealing element releases the airoutlet when the needle unit is inserted and prevents air from enteringafter the needle unit has been positioned and a vacuum has been createdin the biopsy needle interior space.

Due to such an embodiment of the seal, on the one hand air that has beencompressed by inserting the needle unit can escape so that no occludedair bubbles are formed and ultrasound or MR images are not affected ordisrupted.

The use of an appropriately dimensioned hose that is placed over theproximal end of the coaxial hose is a simple, inexpensive, yet effectiveembodiment of the sealing element. Care should be taken that theflexibility of the hose is such that during insertion the suction effectat slight underpressure securely closes the gap present between theinterior wall of the coaxial cannula and the exterior wall of the needleunit. Specifically, this is attained by using suction to draw theproximal end, e.g., the interior edge, of the hose against the exteriorside of the needle unit. For this reason the proximal end of the hose ispreferably slightly curved toward the needle unit so that when thevacuum is created the projecting part of the hose piece is drawn inwardand pressed against the exterior surface of the needle unit. Removingthe vacuum, the underpressure, in the needle hollow space cancels thesealing effect and the gap reopens due to the elasticity of the hose.

However, the sealing element can also be part of the vacuum biopsydevice (e.g., in accordance with DE GMS 202 04 363), in particular whenthe biopsy device is equipped with a guide roller. In this case astopper on the distal side at the guide roller is provided that acts asa sealer to engage a corresponding coupling bore in the cap of thecoaxial cannula. If the sealing elements do not enter into thecounterpart until just prior to the device being placed onto thecounterpart into the countercoupling parts, the air can exit first.Thus, the effect does not occur until just before the closing so that noair bubbles or air occlusions disrupt the ultrasound or MR images.

If an intermediate piece is used between the guide roller and theproximal surface of the coaxial cap to reduce the penetration depth ofthe biopsy needle unit, the intermediate piece has one coupling piece onthe distal side and one on the proximal side so that the stopper of theguide roller can, first, act as a seal, and second, the intermediatepiece can act as a seal in the coupling cap. What is important is thatthe intermediate space between the needle unit and the coaxial cannulais not closed until just prior to the final positioning of the needleunit so that the air can escape and is not compressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are described in detail as follows:

FIG. 1) Exploded depiction of a coaxial cannula with mandrel

FIG. 2) Section through the cap of a coaxial cannula (variant A,enlarged)

FIG. 3) Section through the cap of a coaxial cannula acting togetherwith a guide roller on the biopsy device (variant B, enlarged)

FIG. 4) Section through the coaxial cannula cap using an intermediatepiece and a guide roller on the vacuum biopsy device

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a coaxial cannula with mandrel in an explodeddrawing. A cap 2 is connected to the coaxial cannula tube 1 (“tube” forshort). For attaching the tube 1, the latter projects into an interiorbore 4 of the cap 2 at its proximal end 5 into the cap (FIG. 2). Forexample, a clamping seat holds the proximal tube end 5 in the cap. Asealing element 3, e.g., a hose piece, is placed over the proximal tubeend 5. For inserting the coaxial cannula into the tissue, a mandrel 6(press-in mandrel) is inserted into the coaxial cannula and the mandrelcap 7 is screwed to the cap 2. When assembled, the mandrel tip 8projects beyond the distal end of the tube.

The coaxial cannula is inserted together with the mandrel into thetissue, e.g., by pressing it in, specifically such that, for example bymeans of ultrasound equipment, the mandrel tip of the mandrel is guidedto or placed in the vicinity of the tissue to be examined.

Once the coaxial cannula has been inserted by means of the mandrel, themandrel is withdrawn and removed; e.g., by unscrewing the connection tothe proximal end. In order to prevent rotation or a change in thepositioned coaxial cannula, surfaces are provided on the coaxial cannulain which a fork or clamp that is connected via additional elementsengages, e.g., to the operating or examining table, so that the coaxialcannula is held in the selected position.

After the coaxial cannula has been inserted and positioned, and afterthe mandrel has been removed, the needle unit 9 of a vacuum biopsydevice with or without an externally arranged cutting sleeve 21(specimen separating device) is inserted into the tube 1 of the coaxialcannula (FIG. 2). The needle unit 9 comprises, for example, a hollowneedle with a cutting sleeve 21 that encloses it coaxially and has acutting edge on the distal side. However, the needle apparatus can alsobe an exterior hollow needle in the hollow space of which the cuttingdevice is coaxially arranged. Instead of the mandrel cap, now the endface, for example of a sterile guide roller 13 of the vacuum biopsyequipment, sits against the proximal end face 10 of the cap 2 (see alsoFIGS. 3 and 4). After insertion, the end face of the guide roller 13 ofthe vacuum biopsy device sits on the end face 10 of the cap. When theneedle unit is inserted, the air that penetrated after the removal ofthe mandrel can at first escape until the sealing lip 11 is drawn to theexterior surface of the needle unit by a vacuum created in the hollowneedle; i.e., the part of the sealing element that projects beyond thecannula tube on the proximal side is designed so that when the needleunit is inserted a slight gap remains open between the sealing lip andthe exterior surface of the needle unit; this occurs, for instance, byhaving only one edge 12 of the sealing lip touch the exterior surface.When a vacuum is created in the hollow space of the biopsy needle, theunderpressure increases the pressure force so that the sealing lip 11,that is, the free hose end, is pressed against the exterior surface ofthe needle unit, thus preventing the entry of more air.

In the examples illustrated in FIGS. 3 and 4, alternatives for theembodiment of the sealing function, the guide roller 13 does not sitflush with the end face 10 of the cap, and there is also no sealingelement arranged on the proximal end of the tube 1, but instead theguide roller of the biopsy device has a stopper 14 that is inserted intoa coupling counterpart 15 provided in the cap 2. The stopper seals theexterior surface of the needle unit against the guide roller via theseal 16. The cap is sealed against the stopper of the guide roller bymeans of the seal 17. Both seals are designed, for example, as O-rings.Because the stopper is kept very short in its longitudinal extension(e.g. stopper length is 5 mm), the sealing effect does not occur untiljust prior to placing the guide roller on the cap. In other words, thesealing effect does not occur until just before the needle tip ispositioned. Air that is present in the coaxial cannula can escape untilthe sealing effect occurs. FIG. 4 illustrates the same arrangement asFIG. 3, but in this case in order to reduce the penetration depth of theneedle unit an intermediate piece 18 is inserted between cap 2 and guideroller 13. The intermediate piece has on its distal side a stopper 14that is inserted into the coupling counterpiece. The seal between thecap-side coupling counterpiece of the coaxial cannula and the stopper 14occurs via the seal 19. The stopper 14 of the guide roller is the sameas that already described (FIG. 3) and is inserted into a couplingcounterpiece 20 of the intermediate piece 18, which is arranged on theproximal side. The sealing arrangement is the same as that described forFIG. 3. In this case, as well, the sealing effect does not occur untiljust before the tip of the needle unit is brought into its finalposition. This means that the air that has penetrated can escape fromthe hollow cannula during the insertion process. The intent of bothsolutions is that the air that has penetrated into the coaxial cannulawhen the mandrel is exchanged for the needle unit can escape to thegreatest extent possible when the needle unit is inserted so that nodisruptions occur during the use of ultrasound or MR.

1. A biopsy apparatus, comprising: a coaxial cannula configured forinsertion in tissue with the aid of a mandrel, the coaxial cannulahaving a proximal end and an interior wall; a biopsy needle unitconfigured for insertion into the coaxial cannula after the mandrel isremoved from the coaxial cannula, the biopsy needle unit having anexterior wall, an interior space, and a longitudinally movable specimenseparating device; and a sealing element positioned on the proximal endof the coaxial cannula, the sealing element being configured to enclosean intermediate space between the interior wall of the coaxial cannulaand the exterior wall of the biopsy needle unit, wherein the sealingelement is configured to provide an air outlet of the intermediate spacewhen the biopsy needle unit is inserted into the coaxial cannula and isconfigured to prevent air from entering the intermediate space after theneedle unit has been positioned and a vacuum has been created in theinterior space of the biopsy needle, wherein the sealing element is anelastic member defining a sealing lip and having an interior diameter,the sealing element being pushed over the proximal end of the coaxialcannula, the interior diameter being dimensioned to leave open a gapbetween the sealing lip of the sealing element and the biopsy needleunit, and the elasticity of the sealing element is such that, given anunderpressure in the intermediate space between the exterior wall of thebiopsy needle unit and the interior wall of the coaxial cannula, thesealing lip of the sealing element at the gap comes into contact withthe biopsy needle unit to form a seal against the biopsy needle unit.